Servo-assisted control system for the gears of a double clutch gearbox of a motor vehicle

ABSTRACT

A control system including: first and second actuator devices for controlling the engagement of first and second sets of gears by selection and engagement movements, respectively; a first solenoid valve arranged to put the first or the second actuator device alternatively into communication with a fluid supply; a second solenoid valve arranged to control the selection movements of the actuator device which is in communication with the fluid supply; a distributor interposed between the fluid supply and the actuator devices and displaceable under the control of the first solenoid valve between a first position in which it puts the fluid supply into communication with the first actuator device and a second position in which it puts the fluid supply into communication with the second actuator device; third and fourth proportional pressure solenoid valves arranged to control the engagement movements of the actuator device which is in communication with the fluid supply.

BACKGROUND OF THE INVENTION

The present invention relates to a servo-assisted control system of theelectro-hydraulic type operable to control the shift between the variousgears of a double clutch gearbox of a motor vehicle, in particular asix- or seven-speed gearbox.

A gear control system is known from U.S. patent application No. 013417in the name of the Applicant, which is able to control the displacementof the four engagement sleeves of a six-speed gearbox of a motorvehicle, whether it is of the double clutch type or of the single clutchtype with robotized control. This known system fundamentally comprises:

-   -   a first control device for controlling the displacement of the        coupling sleeves associated with the gears controlled by the        first input shaft of the gearbox, that is to say the first,        third, fifth and sixth gear, as well as the reverse gear; and    -   a second control device for controlling the displacement of the        coupling sleeve associated with the gears controlled by the        second input shaft of the gearbox, that is to say the second and        fourth gear.

The first control device is provided with a drum which is mountedrotatably about its own axis and on the cylindrical lateral surface ofwhich are provided three control grooves each of which engages arespective pin to displace it in the direction of the axis of the drumupon rotation of this latter. The three pins are each connected to arespective fork which controls the displacement of a respective couplingsleeve. The second control device is provided with a slidable rodcarrying a fork for control of the displacement of the coupling sleeveof the second and fourth gear.

According to a first embodiment this known control system iselectrohydraulically operated. The two control devices are alternativelycontrolled by a first proportional solenoid valve which controls the upshifting, and by a second proportional solenoid valve which controls thedown shifting. The two solenoid valves modulate the pressure of theworking fluid supplied by a pump in a delivery line and alternativelyconnect a first and a second input line of a six-way distributor withthe delivery line from the pump or with a discharge line. The six-waydistributor is further connected to the hydraulic actuator of the firstcontrol device through third and fourth output lines and to thehydraulic actuator of the second control device through fifth and sixthoutput lines.

This known control system, in combination with the double clutchsix-speed gearbox described in the above document, makes it possible toperform multiple gear changes in “power shift” mode during the followingdownshift maneuvers: from sixth to fourth or to second; from fifth tosecond; and from fourth to first. The remaining multiple downshiftmaneuvers can however be performed in a traditional manner, that is withinterruption of torque transmission.

A further example of a servo-assisted control system for the gears of asix-speed double clutch gearbox for a motor vehicle is known from GermanPatent Application DE 101 34 115. This known control system includes ahydraulic circuit arranged to control four double-acting hydrauliccylinders for actuation of four coupling sleeves, that is to say a firstsleeve which effects engagement of the first or third gear, a secondsleeve which effects engagement of the fifth gear, a third sleeve whicheffects engagement of the second or fourth gear and a fourth sleevewhich effects engagement of the sixth gear or the reverse gear. Thehydraulic circuit is subdivided into a first portion intended to controlthe odd gears and a second portion intended to control the even gearsand the reverse gear. Upstream of each circuit portion is disposed apilot valve which controls the supply of oil under pressure to therespective circuit portion. Each circuit portion includes a pair ofproportional solenoid valves which control the two double-actinghydraulic cylinders to actuate the coupling sleeves of the gearsassociated with this circuit portion. Between the four double-actinghydraulic cylinders and the four proportional solenoid valves associatedtherewith is interposed a distributor.

This known control system makes it possible to perform multiple gearchanges in “power shift” mode directly (that is non-sequentially)between gears not associated with the same input shaft of the gearbox.It has, however, the disadvantage of requiring a large number ofcomponents and of therefore having a high cost.

SUMMARY OF THE INVENTION

The object of the invention is to provide an electro-hydraulic controlsystem for a six or more speed gearbox of a motor vehicle, whether ofthe double-clutch or of the single-clutch type with robotized control,which has a smaller number of components and therefore a lower cost thanthe prior art, which makes it possible to perform the greatest possiblenumber of multiple gear changes in “power shift” mode directly (that isnon-sequentially) available from the gearbox architecture, and which iseasily adaptable to different gearbox versions in such a way as to allowa further reduction in the costs of production.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and advantages of the invention will become clearlyapparent from the following detailed description, given purely by way ofnon-limitative example with reference to the attached drawings, inwhich:

FIG. 1 is a schematic illustration of a first embodiment of aservo-assisted gearbox control system according to the presentinvention;

FIG. 2 is a view in axial section of a known seven-speed double clutchgearbox for which the control system of FIG. 1 is intended;

FIG. 3 is a schematic view which shows the two actuators of the controlsystem of FIG. 1 together with the respective coupling members;

FIG. 4 is a view on the arrow F of FIG. 3 which shows the threeengagement fingers associated with the actuator for controlling the oddgears and the reverse gear of the control system of FIG. 1;

FIG. 5 is a view on the arrow F of FIG. 3 which shows the two engagementfingers, associated with the actuator for controlling the even gears ofthe control system of FIG. 1;

FIGS. 6A to 6H show the sequence of operations necessary to effect theengagement of seventh gear starting from the neutral condition betweenthe first and third gear of the control system of FIG. 1;

FIGS. 7 and 8 are schematic illustrations of a second and, respectively,a third embodiment of a servo-assisted gear shift control system for agearbox according to the present invention, both intended for asix-speed double clutch gearbox derived from the seven-speed gearbox ofFIG. 2;

FIG. 9 is a schematic illustration of a fourth embodiment of aservo-assisted gear shift control system for a gearbox according to thepresent invention, intended for a robotized seven-speed single clutchgearbox derived from the seven-speed gearbox of FIG. 2; and

FIG. 10 is a schematic illustration of a fifth embodiment of aservo-assisted gear shift control system for a gearbox, according to thepresent invention, intended for a robotized six-speed single clutchgearbox derived from the seven-speed gearbox of FIG. 2.

Parts and components associated with the various forward gears of thegearbox are indicated in the drawings with the Roman numerals I, II,III, IV, V, VI and VII, respectively, for the first, second, third,fourth, fifth, sixth and seventh gear, whilst parts and componentsassociated with the reverse gear are indicated with the letter R.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 2 shows in axial section a seven-speed double clutch gearbox for amotor vehicle forming the subject of European Patent Application No.04425283.1 in the name of the Applicant.

The gearbox of FIG. 2 comprises a first coupling sleeve 141 selectivelydisplaceable to left and right to engage the first and the third gear,respectively, a second coupling sleeve 142 selectively displaceable toleft and right to engage the seventh and sixth gear, respectively, athird coupling sleeve 143 selectively displaceable to left and right toengage the reverse gear and the fifth gear, respectively, and a fourthcoupling sleeve 144 selectively displaceable to left and right to engagethe second and fourth gear, respectively. The four coupling sleeves141-144 are of type known per se and therefore will not be described indetail.

The gearbox of FIG. 2 makes it possible to perform all the sequentialgear shifts in “power shift” mode, except that between the sixth andseventh gear, the engagement of these two gears being controlled by thesame sleeve 142. Moreover, this gearbox makes it possible to performmultiple gear changes in “power shift” mode during the followingdownshift maneuvers, from seventh to fourth or second, from sixth tothird or first, from fifth to second and from fourth to first.

The engagement of the different gears of the gearbox of FIG. 2 can beeffected, according to a first embodiment of the invention, by means ofthe control system schematically shown in its entirely in FIG. 1.

With reference to FIG. 1, the control system fundamentally comprises afirst actuator device 11 intended to control the displacement of thecoupling sleeves 141, 142 and 143 in order selectively to engage one ofthe gears controlled by a first input shaft 110 of the gearbox, that isto say first, third, fifth, seventh and reverse, and a second actuatordevice 12 intended to control the displacement of the coupling sleeves142 and 144 in order selectively to engage one of the gears controlledby a second input shaft 112, that is to say second, fourth and sixth. Asschematically illustrated in FIG. 2 and as will be explained in detailhereinafter, the second coupling sleeve 142 associated with the sixthand seventh gear is controlled by a single fork indicated 27, on whichboth actuator devices 11 and 12 can act. Preferably, the first actuatordevice 11 is of the so-called S-cam type, whilst the second actuatordevice 12 is of the twin axis type.

Referring now also to FIG. 3, the actuator device 11 comprises, in amanner known per se, a shaft 14 with axis x1 (perpendicular to the axesof the input shafts 110 and 112 of the gearbox) and a cylinder 16disposed coaxially to the shaft 14 and having an S-shape groove 18. Theshaft 14 can turn about its axis x1 (as indicated by the arrow R1) andtranslate in the direction of its axis (as indicated by the arrow T1).The cylinder 16 on the other hand can only translate in the direction ofits axis x1, as indicated by the arrow Z1. A pin 20 drivingly connectedto the shaft 14 engages in the groove 18 of the cylinder 16 so as toconnect the rotation and translation movements of the shaft with thetranslation of the cylinder. The shaft 14 is further provided with twoengagement fingers 21 and 22 and a control lever 23 drivingly connectedthereto. The first engagement finger 21 is arranged to engage in anengagement window 24 of a first actuating fork 25 associated with thefirst sleeve 141 (first and third gear) or in an engagement window 26 ofa second actuating fork 27 associated with the second sleeve 142 (sixthand seventh gear). The second engagement finger 22 is arranged to engagein an engagement window 28 of a third actuating fork 29 associated withthe third sleeve 143 (fifth gear and reverse gear). The two engagementfingers 21 and 22 are disposed along the shaft 14 in such a manner thateach time only one of these is aligned with one of the three engagementwindows 24, 26 and 28. The S-shape groove 18 of the cylinder 16comprises a pair of straight sections 18 a and 18 b, which extendtransversely of the axis x1 on opposite sides with respect to thislatter and are spaced from one another in the direction of the axis x1by a distance equal to the rank of the gears, and an inclined section 18c which joins the two straight sections 18 a and 18 b.

The rotation of the shaft 14 is controlled by a double-acting hydraulicactuator 30 via the control lever 23. The cylinder 16 is axiallylockable by means of a locking device 32 formed for example as asingle-acting hydraulic actuator, which in the rest condition leaves thecylinder free to translate axially along its axis. The two chambers ofthe hydraulic actuator 30 are connected to a three-input and six-outputdistributor 34 via a first output line OL1 and a second output line OL2.On the other hand, a third output line OL3 from the distributor 34 isconnected to the actuator 32. The distributor 34 is connected to asupply of fluid under pressure (not illustrated) via a first input lineIL1, in which is disposed a first proportional pressure solenoid valve35, via a second input line IL2, in which is disposed a secondproportional pressure solenoid valve 36, and via the third input lineIL3, in which is disposed an ON/OFF solenoid valve 37. The distributor34 is normally in a first working position such that the input line IL1is connected to the output line OL1, the input line IL2 is connected tothe output line OL2 and the input line IL3 is connected to the outputline OL3. In this way, the actuator 30 is controlled by means of the twoproportional solenoid valves 35 and 36 in order to control the rotationof the shaft 14 of the first actuator device 11, whilst the actuator 32is controlled by means of the ON/OFF solenoid valve 37 in order to lockor release the axial movement of the cylinder 16.

In FIG. 1 the control system is shown in the neutral condition betweenthe first and third gear, in which the first engagement finger 21 isaxially aligned with the engagement window 24 of the actuating fork 25associated with the sleeve 141 of first and third gear and is disposedwith clearance within this window. In this condition the pin 20 of theshaft 14 is positioned half way along the inclined section 18 c of thegroove 18 of the cylinder 16.

If, now, the shaft 14 is driven to rotate anticlockwise as viewed from Fin FIGS. 1 and 3, by supplying fluid under pressure to the actuator 30via lines IL1 and OL1 under the control of the solenoid valve 35 (insuch a manner that the actuator 30 translates rightwards with respect tothe observer of FIG. 1), the pin 20, which is drivingly connected to theshaft 14, forces the cylinder 16, which can translate axially as thelocking device 32 is not active, to slide along the inclined section 18c of the groove 18, thus causing upward displacement of this latter.Moreover, the engagement finger 21, which rotates rigidly with the shaft14, causes the fork 25, together the sleeve 141, to move leftwards thusengaging the first gear. If, on the other hand, starting from theneutral condition the shaft 14 is driven to rotate in the clockwisesense, the third gear is engaged. As is clearly shown in FIG. 1, theengagement window 24 of the fork 25 associated with the first and thirdgear has a width significantly greater than the other two engagementwindows 26 and 28. The clearance between the engagement finger 21 andthe engagement window 24 is therefore correspondingly greater than thatbetween the same finger and the engagement window 26 (associated withthe seventh gear) or between the engagement finger 22 and the engagementwindow 28 (associated with the fifth gear and the reverse gear). Thismakes is possible to give the shaft 24 a small rotation in one directionor the other, starting from the neutral position between first andthird, without thereby causing the engagement of the first or thirdgear. These two engagement start positions of the first and third gearserve during the engagement phases of the fifth and seventh gear,respectively, as will be explained in detail hereinafter.

Referring now to FIGS. 6A to 6H, the engagement operation of the seventhgear will now be described. Starting from the neutral position betweenthe first and third gear (FIG. 6A) the shaft 14 is driven to rotateclockwise through only such an angle as to cancel the clearance betweenthe engagement finger 21 and the corresponding engagement window 24(FIG. 6B). Passing from the condition of FIG. 6A to the condition ofFIG. 6B, the pin 20 of the shaft 14 rotates until reaching the point atwhich the horizontal section 18 b of the groove 18 starts, whilst due tothe inclined section 18 c of the groove 18 the cylinder 16 translatesaxially downwards. At this point the locking device 32 is actuated bymeans of the solenoid valve 37 so as axially to lock the cylinder 16.Then the shaft 14 is driven to rotate again, but this timeanticlockwise. Since the cylinder 16 is locked, the pin 20 slides alongthe whole inclined section 18 c of the groove 18 from the upperhorizontal section 18 b to the lower horizontal section 18 a, thuscausing the shaft 14 to translate downwards one rank in such a way as toalign the engagement finger 21 axially with the window 26 of the fork 27of seventh gear (FIG. 6F). At this point, by continuing with theanticlockwise rotation of the shaft 14, the pin 20 moves along thehorizontal section 18 a of the groove 18, whilst the engagement finger21 causes the fork 27 to move leftwards together with the sleeve 142,thus engaging the seventh gear (FIG. 6H).

The engagement of the fifth gear starting from the neutral condition ofFIG. 1 takes place in a symmetric manner to that of the seventh gear (itbeing necessary in this case to drive the shaft 14 to rotateanticlockwise rather than clockwise, by using the solenoid valve 35) andwill therefore not be described in detail.

To engage the reverse gear starting from the neutral condition of FIG. 1the following operations are performed in sequence:

-   -   anticlockwise rotation of the shaft 14 up to the position of        start of the engagement of the first gear in such a way as to        displace the cylinder 16 axially upwards;    -   locking of the cylinder 16;    -   clockwise rotation of the shaft 14 up to the position of start        of the engagement of the fifth gear, in such a way as to        displace the shaft 14 axially until the engagement finger 22 is        brought into alignment with the engagement window 28 of the fork        29 associated with the fifth gear and the reverse gear;    -   release of the cylinder 16; and    -   anticlockwise rotation of the shaft 14 in such a way as to        displace the fork 29, together with the sleeve 143, leftwards to        engage the reverse gear.

Returning to FIG. 1, the second actuator device 12 comprises a shaft 40mounted so as to rotate about its axis x2 (as indicated by the arrow R2)and translate in the direction of its axis (as indicated by the arrowT2). The shaft 40 is provided with two engagement fingers 41 and 42drivingly connected thereto, of which the first engagement finger 41 isarranged to engage in an engagement window 44 of a fourth actuating fork45 associated with the fourth sleeve 144 (second and fourth gear),whilst the second engagement finger 42 is arranged to engage in afurther engagement window 46 provided on the second actuating fork 27associated with the second sleeve 142 (sixth and seventh gear).

The shaft 40 is normally held, for example by the resilient action of aspring 48, in a position such that its first engagement finger 41 isaxially aligned with the respective engagement window 44 (neutralcondition between the second and fourth gear), whilst its secondengagement finger 42 is positioned outside the respective engagementwindow 46. A single-acting hydraulic actuator 50 is arranged to displacethe shaft 40 axially against the action of the spring 48 in such a wayas to bring the first engagement finger 41 out of the respective window44 and to align the second engagement finger 42 with the respectivewindow 46 to permit engagement of the sixth gear. The rotationalmovement of the shaft 40 about its axis x2 (gear engagement movement) iscontrolled by a double-acting hydraulic actuator 52, advantageouslyidentical to the actuator 30 of the first control device 11, through acontrol lever 53 on the shaft 40, advantageously identical to thecontrol lever 23 on the shaft 14 of the first device 11.

The two chambers of the double-acting hydraulic actuator 52 areconnected to the distributor 34 via a fourth output line OL4 and a fifthoutput line OL5, whilst the single-acting hydraulic actuator 50 isconnected to the distributor 34 via a sixth output line OL6. Thedistributor can be controlled by an ON/OFF pilot solenoid valve 54 to bedisplaced to a second working position in which the input line IL1 isconnected to the output line OL4, the input line IL2 is connected to theoutput line OL5 and the input line IL3 is connected to the output lineOL6. In this way, by means of the two pressure proportional solenoidvalves 35 and 36 in the two input lines IL1 and IL2, the actuator 52 iscontrolled to drive the shaft 40 to rotate, whilst by means of theON/OFF solenoid valve 37 in the third input line IL3 the actuator 50 iscontrolled to displace the shaft 40 axially towards the selectionposition for the sixth gear.

In FIG. 1 the second control device 12 is shown in the neutral conditionbetween the second and fourth gear. If the shaft 40 is now rotatedanticlockwise (as viewed from F in FIGS. 1 and 3), by supplying fluidunder pressure to the actuator 52 via the lines IL1 and OL4 under thecontrol of the solenoid valve 35, the engagement finger 41, whichrotates rigidly with the shaft 40, causes the fork 45 to displaceleftwards together with the sleeve 144, thus engaging the second gear.If, on the other hand, starting from the neutral condition the shaft 40is rotated clockwise, engagement of the fourth gear is obtained. Toengage the sixth gear it is necessary first to displace the shaft 40axially into the sixth gear selection position (condition of alignmentof the engagement finger 42 with the engagement window 46 of the fork27), by supplying fluid under pressure to the actuator 50 through thelines IL3 and OL6 under the control of the solenoid valve 37. At thispoint the shaft 40 is rotated clockwise by supplying fluid underpressure to the actuator 52 through the lines IL2 and OL5 under thecontrol of the solenoid valve 36, in such a way that the engagementfinger 42 displaces the fork 27, together with the sleeve 142,rightwards.

Thanks to the fact that the fork 27 which actuates the sleeve 142 ofsixth and seventh gear is alternatively controllable by both the controldevices 11 and 12, the control system makes it possible to perform thegreatest possible number of multiple gear shifts in “power shift” mode,starting from the seventh or sixth gear. In fact, starting from thecondition of engagement of the seventh gear (by means of the firstcontrol device 11), the second control device 12 can simultaneouslyengage the second or fourth gear in such a way as to permit the directchange from the seventh gear to the fourth or second gear in “powershift” mode. The same gear change possibilities are offered startingfrom the fifth gear.

On the other hand, starting from the condition of engagement of thesixth gear (by means of the second control device 12), the first controldevice 11 can simultaneously engage the third or first gear in such away as to permit the direct change from the sixth gear to the third orfirst gear in “power shift” mode. The same gear change possibilities areoffered starting from the fourth gear.

Moreover, thanks to the fact that an initial condition of the controlsystem is provided in which the first control device 11 is in theneutral position between the first and third gear and the second controldevice 12 is in the neutral position between the second and fourth gear,it is possible to perform the first four gear changes (from the neutralposition to the fourth gear) without the need to perform any selectionmovement (axial displacement of the shafts 14 and 40 of the two controldevices). It is in fact sufficient to control the pilot solenoid valve54 to select the shafts 14 or 40 to control and the two proportionalsolenoid valves 35 and 36 to drive the selected shaft to rotate in onedirection or the other.

To avoid the risk of an erroneous engagement of a gear by one of the twocontrol devices, in particular the simultaneous engagement on two gearsof the same input shaft of the gearbox, a safety system or so-called“interlock” system is provided which will now be illustrated in detail.With reference to FIG. 3, the “interlock” system comprises a firstsafety device 61 mounted on the shaft 14 of the first control device 11and a second safety device 62 mounted on the shaft 40 of the secondcontrol device 12. Each safety device 61, 62 is displaceable along theaxis x1, x2 of the respective shaft 14, 40 as a result of the axialtranslation movement imparted to this latter, and is locked againstrotation by means of a restraint (not shown) provided by a fixed part ofthe gearbox.

The first safety device 61 forms a first arm 63 carrying an axialprojection 64 engageable in the engagement window 24 of the fork 25 offirst and third gear, a second arm 65 carrying an axial projection 66engageable in the engagement window 26 of the fork 27 of sixth andseventh gear and a third arm 67 carrying an axial projection 68engageable in the engagement window 28 of the fork 29 of reverse gearand fifth gear. Similarly, the second safety device 62 forms a first arm69 carrying an axial projection 70 engageable in the engagement window44 of the fork 45 of second and fourth gear and a second arm 71 carryingan axial projection 72 engageable in the other engagement window 46 ofthe fork 27 of sixth and seventh gear.

The three axial projections 64, 66 and 68 of the first safety device 61are formed in such a way that each time two of them engage in thecorresponding engagement windows, thus preventing the actuation of therespective fork, whilst the third projection disengages from thecorresponding engagement window, which can therefore be engaged by thecorresponding engagement finger. For example, in the operating conditionillustrated in FIG. 1 the projection 66 occupies the engagement window26 of the fork 27, thus preventing unwanted displacement of this forkwhich would cause engagement of the seventh gear. The projection 68occupies the engagement window 28 of the fork 29, thus preventingunwanted displacement of this fork which would cause engagement of thereverse gear or fifth gear. The projection 64 is, on the other hand,disengaged from the engagement window 24 of the fork 25 in such a way asto allow the engagement finger 21 to engage the first or third gear. Thesame applies to the second safety device 62.

The “interlock” system is further suitably configured to preventsimultaneous actuation of the fork 27 of sixth and seventh gear by thetwo control devices 11 and 12. To this end, as shown in the diagram ofFIG. 1, the projections 66 and 72 of the two safety devices 61 and 62associated with the fork 27 are arranged to cooperate with respectiveabutment surfaces 27 a and 27 b formed on the fork 27 in such a mannerthat:

-   -   when the two control devices 11 and 12 are one in the neutral        position between the first and third gear and the other in the        neutral position between the second and fourth gear the        projection 66 faces the abutment surface 27 a so as to prevent        leftwards displacement of the fork 27 and therefore engagement        of the seventh gear, and likewise the projection 72 faces the        abutment surface 27 b so as to prevent rightwards displacement        of the fork 27 and therefore engagement of the sixth gear;    -   when the shaft 14 of the first control device 11 is displaced        axially (downwards) into the seventh gear selection position,        the projection 66 moves away from the abutment surface 27 a        leaving the fork 27 free to displace leftwards to engage the        seventh gear, whilst the projection 72 continues to prevent        rightwards displacement of the fork 27 and therefore erroneous        engagement of the sixth gear; and    -   when the shaft 40 of the second control device 12 is displaced        axially (downwards) into the sixth gear selection position, the        projection 72 moves away from the abutment surface 27 b leaving        the fork 27 free to displace rightwards to engage the sixth        gear, whilst the projection 66 continues to prevent leftwards        displacement of the fork 27 and therefore erroneous engagement        of the seventh gear.

The control device 11 is further provided with a first detent mechanism80 shown in FIG. 3, which controls the axial positioning of the shaft 14by defining a first intermediate selection position of the fork 25 offirst and third gear, a second selection position of the fork 27 ofseventh and sixth gear and a third selection position of the fork 29 ofreverse and fifth gear. The detent mechanism 80 comprises, in a mannerknown per se, a slidable segment 81 fixed to the shaft 14 and havingthree engagement seats corresponding to the said three selectionpositions (ranks) of the shaft 14 and a ball 82 intended to snap-engageunder the action of a spring (not illustrated) into one of these seats.The shaft 14 is further provided with a second detent mechanism 85,shown in FIGS. 3 and 4, which controls the angular positioning of theshaft 14 by defining a central neutral position and two oppositeengagement positions. The detent mechanism 85 comprises, in a mannerknown per se, a catch element 86 fixed to the shaft 14 and having acentral engagement seat 87 corresponding to the neutral position and apair of lateral engagement surfaces 88 corresponding to the engagementpositions, and a ball 89 intended to snap-engage, under the action of aspring (not illustrated) into the seat 87 or against one of the surfaces88.

The second control device 12 is provided with a detent mechanism 90,similar to the detent mechanism 85 of the first control device 11, whichcontrols the angular positioning of the shaft 40. The mechanism 90comprises a catch element 91, fixed to the shaft 40 and having a centralengagement seat 92 corresponding to the neutral position and a pair oflateral engagement surfaces 93 corresponding to the engagementpositions, and a ball 94 intended to snap-engage under the action of aspring (not illustrated) into the seat 92 or against one of the surfaces93.

Position sensors (not illustrated) are also provided on the first andsecond control devices 11 and 12 for providing signals indicative of theaxial position (to identify the rank) and the angular position (toidentify the neutral position or the engaged gear) of the two shafts 14and 40.

A second embodiment of a gearbox control system according to theinvention, intended to control a six-speed double clutch gearboxobtained from the gearbox of FIG. 2 simply by eliminating the seventhgear driven wheel on the first output shaft, is schematicallyillustrated in FIG. 7, where parts and elements identical orcorresponding to those of FIG. 1 have been given the same referencenumerals. The actuator devices 11, 12 and the hydraulic circuit whichcontrols the supply of fluid under pressure to the two devices aresubstantially identical to those of the control system of FIG. 1 andwill therefore not be described in detail. The only difference withrespect to the first embodiment is that the first actuator device 11 isarranged to control only the coupling sleeve of first and third gear andthe coupling sleeve of fifth gear and reverse gear.

A third embodiment of the invention, also intended to control asix-speed double clutch gearbox obtained from the gearbox of FIG. 2, isschematically illustrated in FIG. 8, where parts and elements identicalor corresponding to those of FIG. 1 have been given the same referencenumerals. As opposed to the second embodiment of FIG. 7, in this casethe actuator devices 11 and 12 which control the engagement of the oddgears (as well as the reverse gear) and of the even gears, respectively,are both of the twin axis type.

The second actuator device 12, as well as the hydraulic circuit whichcontrols the supply of fluid under pressure to the two devices 11 and12, are substantially identical to those of the first embodiment of FIG.1, and will therefore not be described in detail.

The first actuator device 11 comprises a shaft 14 which can rotate aboutits axis x1 (as indicated by the arrow R1) and translate in thedirection of this axis (as indicated by the arrow T1). The shaft 14 isprovided with two engagement fingers 21 and 22 drivingly connectedthereto, of which the first engagement finger 21 is arranged to engagein the engagement window 24 of the actuating fork 25 associated with thefirst and third gear, whilst the second engagement finger 22 is arrangedto engage in the engagement window 28 of the actuating fork 29associated with the fifth gear and the reverse gear.

The shaft 14 is normally held, for example by the resilient action of aspring 47, in such a position that its first engagement finger 21 isaxially aligned with the respective engagement window 24 (neutralcondition between the first and third gear), whilst its secondengagement finger 22 is positioned outside the respective engagementwindow 28. A single-acting hydraulic actuator 49 is arranged to displacethe shaft 14 axially against the action of the spring 47 in such a wayas to bring the first engagement finger 21 out of the respective window24 and to align the second engagement finger 22 with the respectivewindow 28 for engagement of the reverse gear or the fifth gear. Therotational movement of the shaft 14 about its axis x1 (gear engagementmovement) is controlled by a double-acting hydraulic actuator 51. Thetwo chambers of the double-acting hydraulic actuator 51 are connected tothe distributor 34 of the hydraulic control circuit via the output linesOL1 and OL2, respectively, whilst the single-acting hydraulic actuator49 is connected to the distributor 34 via the output line OL3.

Advantageously, the two actuator devices 11 and 12 are identical to oneanother in such a way as further to reduce the overall cost of thecontrol system.

A fourth embodiment of a gearbox control system according to theinvention will now be briefly described, the system being intended tocontrol a seven-speed single clutch robotized gearbox derived from thegearbox of FIG. 2. This embodiment is schematically illustrated in FIG.9, where parts and elements identical or corresponding to those of FIG.1 have been given the same reference numerals.

Since the simultaneous engagement of two gears is not required, a singlecontrol device 11 of the S-cam type is sufficient to engage all thegears. The control device 11 is structurally identical to thatpreviously described with reference to the embodiment of FIG. 1. In thiscase, however, a first engagement finger 21 is arranged to engagealternatively in an engagement window 24 of a first actuating fork 25 offirst and second gear or in an engagement window 26 of a secondactuating fork 27 of sixth and seventh gear. A second engagement finger22 is arranged to engage alternatively in an engagement window 44 of athird actuating fork 45 of third and fourth gear or in an engagementwindow 28 of a fourth actuating fork 29 of fifth gear and reverse gear.

The rotation of the shaft 14 (engagement movement) is controlled by adouble-acting hydraulic actuator 30 which is connected to a supply offluid under pressure via first and second lines IL1 and IL2 in each ofwhich is disposed a respective proportional pressure solenoid valve 35and 36. To lock the axial movement of a cylinder 16 of the controldevice 11 there is provided a locking device 32 formed for example as asingle-acting hydraulic actuator controlled by an ON/OFF solenoid valve37 via a third line IL3.

Finally, a fifth embodiment of a gearbox control system according to theinvention, intended to control a six-speed single clutch robotizedgearbox derived from the gearbox of FIG. 2, is schematically illustratedin FIG. 10, where parts and elements identical or corresponding to thoseof FIG. 7 have been given the same reference numerals. This fifthembodiment differs from the fourth substantially only in the arrangementof the engagement windows, and will not therefore be described indetail.

The servo-assisted control system according to the invention hastherefore the advantage of requiring a smaller number of solenoid valvesthan the prior art with the same operable functions (the possibility ofperforming directly several multiple gear shifts in “power shift” modeand the possibility of directly or indirectly performing the remainingmultiple gear shifts, even if not in “power shift” mode). The followingfour solenoid valves are in fact sufficient:

-   -   the ON/OFF solenoid valve 54 which controls the positioning of        the distributor 34;    -   the ON/OFF solenoid valve 37 which controls the locking device        32 of the first actuator device 11 to control the selection        movement for the gears associated with this device and which, in        the case of a double clutch gearbox, also controls the axial        positioning of the shaft 40 of the second actuator device 12        (selection movement);    -   the two proportional pressure solenoid valves 35 and 36 which        control the engagement movements of the first actuator device 11        and, in the case of a double clutch gearbox, also of the second        actuator device 12.

In the case of a control system intended for a double clutch gearbox thetwo actuator devices, respectively of the S-cam and of the twin axistype, use the maximum possible number of components in common, whichallows to reduce the overall cost of the system. Moreover, both thecontrol system intended for a double clutch gearbox and that intendedfor a single clutch gearbox preferably use an actuator device of theS-cam type. The two control systems can therefore share a large numberof components and thus be fabricated in the same productioninstallation.

The gear control system according to the invention further has a highflexibility of configuration, as it can be adapted to control a six- orseven-speed double clutch gearbox, or a robotized six- or seven-speedsingle clutch gearbox.

The gear control system according to the invention can further beprovided as an ADD-ON version, in such a manner as to increase thepossibilities of application with minimum modification to the manualgearbox.

1. A servo-assisted control system for a double clutch gearbox of motorvehicle having six or seven forward gears and a reverse gear, the systemcomprising: a first hydraulically-operated actuator device forcontrolling the engagement of a first set of gears by selection andengagement movements; a second hydraulically-operated actuator devicefor controlling the engagement of a second set of gears by selection andengagement movements; a first solenoid valve arranged to selectively andalternatively put the first and the second actuator device intocommunication with a supply of fluid under pressure; a second solenoidvalve arranged to control the selection movements of said first actuatordevice when it is in communication with the fluid supply and to controlthe selection movements of said second actuator devices when it is incommunication with the fluid supply; and a third proportional pressuresolenoid valve and a fourth proportional pressure solenoid valvearranged to control the engagement movements of said first actuatordevice when it is in communication with the fluid supply and to controlthe engagement movements of said second actuator device when it is incommunication with the fluid supply; in such a way that a gear changeoperation requires the intervention of at most four solenoid valves. 2.A control system according to claim 1, further including a distributorinterposed between the pressure fluid supply and said first and secondactuator devices, the distributor being displaceable under the controlof the first solenoid valve between a first working position in whichthe distributor puts the pressure fluid supply into communication withthe first actuator device and a second working position in which thedistributor puts the pressure fluid supply into communication with thesecond actuator device.
 3. A control system according to claim 1, inwhich the said first and second solenoid valves are of the ON/OFF type.4. A control system according to claim 1, in which the first actuatordevice controls the engagement of the odd gears and of the reverse gearand the second actuator device controls the engagement of the evengears.
 5. A control system according to claim 1, in which the firstactuator device is a S-cam actuator device.
 6. A control systemaccording to claim 1, in which the second actuator device is a twin axisactuator device.